From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 38A42C43381 for ; Wed, 13 Mar 2019 17:23:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0631C21019 for ; Wed, 13 Mar 2019 17:23:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725926AbfCMRXr (ORCPT ); Wed, 13 Mar 2019 13:23:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:48024 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725895AbfCMRXr (ORCPT ); Wed, 13 Mar 2019 13:23:47 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C061D21019; Wed, 13 Mar 2019 17:23:45 +0000 (UTC) Date: Wed, 13 Mar 2019 13:23:44 -0400 From: Steven Rostedt To: Tzvetomir Stoyanov Cc: linux-trace-devel@vger.kernel.org Subject: Re: [PATCH v4 16/46] tools/lib/traceevent: Man pages for tep_register_print_function() and tep_unregister_print_function() Message-ID: <20190313132344.5f58e940@gandalf.local.home> In-Reply-To: <20190308133654.21264-17-tstoyanov@vmware.com> References: <20190308133654.21264-1-tstoyanov@vmware.com> <20190308133654.21264-17-tstoyanov@vmware.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-trace-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On Fri, 8 Mar 2019 15:36:24 +0200 Tzvetomir Stoyanov wrote: > Create man pages for tep_register_print_function() and tep_unregister_print_function() > as part of the libtraceevent APIs. > > Signed-off-by: Tzvetomir Stoyanov > --- > .../libtraceevent-reg_print_func.txt | 128 ++++++++++++++++++ > 1 file changed, 128 insertions(+) > create mode 100644 tools/lib/traceevent/Documentation/libtraceevent-reg_print_func.txt > > diff --git a/tools/lib/traceevent/Documentation/libtraceevent-reg_print_func.txt b/tools/lib/traceevent/Documentation/libtraceevent-reg_print_func.txt > new file mode 100644 > index 000000000000..59cef18b71f1 > --- /dev/null > +++ b/tools/lib/traceevent/Documentation/libtraceevent-reg_print_func.txt > @@ -0,0 +1,128 @@ > +libtraceevent(3) > +================ > + > +NAME > +---- > +tep_register_print_function,tep_unregister_print_function - Registers / Unregisters > +a helper function. > + > +SYNOPSIS > +-------- > +[verse] > +-- > +*#include * > + > +enum *tep_func_arg_type* { > + TEP_FUNC_ARG_VOID, > + TEP_FUNC_ARG_INT, > + TEP_FUNC_ARG_LONG, > + TEP_FUNC_ARG_STRING, > + TEP_FUNC_ARG_PTR, > + TEP_FUNC_ARG_MAX_TYPES > +}; > + > +typedef unsigned long long (*pass:[*]tep_func_handler*)(struct trace_seq pass:[*]s, unsigned long long pass:[*]args); > + > +int *tep_register_print_function*(struct tep_handle pass:[*]_tep_, tep_func_handler _func_, enum tep_func_arg_type _ret_type_, char pass:[*]_name_, _..._); > +int *tep_unregister_print_function*(struct tep_handle pass:[*]_tep_, tep_func_handler _func_, char pass:[*]_name_); > +-- > + > +DESCRIPTION > +----------- > +Some events may have helper functions in the print format arguments. This allows > +a plugin to dynamically create a way to process one of these functions. > + > +The _tep_register_print_function()_ registers such helper function. The _tep_ > +argument is the trace event parser context. The _func_ argument is the address > +of the helper function. The _ret_type_ argument is the return type of the I would say "The _func_ argument is a pointer to the helper function". > +helper function, value from the _tep_func_arg_type_ enum. The _name_ is the name > +of the helper function, as seen in the print format arguments. The _..._ is a > +variable list of _tep_func_arg_type_ enums, the _func_ function arguments. > +This list must end with _TEP_FUNC_ARG_VOID_. We should elaborate more what this is for. Some events have internal functions called that appear in the print format output. For example, tracefs/events/i915/g4x_wm/format has: print fmt: "pipe %c, frame=%u, scanline=%u, wm %d/%d/%d, sr %s/%d/%d/%d, hpll %s/%d/%d/%d, fbc %s", ((REC->pipe) + 'A'), REC->frame, REC->scanline, REC->primary, REC->sprite, REC->cursor, yesno(REC->cxsr), REC->sr_plane, REC->sr_cursor, REC->sr_fbc, yesno(REC->hpll), REC->hpll_plane, REC->hpll_cursor, REC->hpll_fbc, yesno(REC->fbc) Where inside the kernel they define a function: static const char *yesno(int x) { static const char *yes = "yes"; static const char *no = "no"; return x ? yes : no; } Now the event parser has no idea how to handle this "yesno()" function. But if we have: static const char *yesno(int x) { return x ? "yes" : "no"; } tep_register_print_function(tep, yesno, TEP_FUNC_ARG_STRING, "yesno", TEP_FUNC_ARG_INT, TEP_FUNC_ARG_VOID); Then when the parser encounters this "yesno()" function, it will know how to handle it. This actually is a good example to use in the man page! -- Steve > + > +The _tep_unregister_print_function()_ unregisters a helper function, previously > +registered with _tep_register_print_function()_. The _tep_ argument is the > +trace event parser context. The _func_ and _name_ arguments are the same, used > +when the helper function was registered. > + > +The _tep_func_handler_ is the type of the helper function. The _s_ argument is > +the trace sequence, it can be used to create a custom string. > +The _args_ is a list of arguments, defined when the helper function was > +registered. > + > +RETURN VALUE > +------------ > +The _tep_register_print_function()_ function returns 0 in case of success. > +In case of an error, TEP_ERRNO_... code is returned. > + > +The _tep_unregister_print_function()_ returns 0 in case of success, or -1 in > +case of an error. > + > +EXAMPLE > +------- > +[source,c] > +-- > +#include > +#include > +... > +struct tep_handle *tep = tep_alloc(); > +... > +static long long > +process_custom_helper(struct trace_seq *s, unsigned long long *args) > +{ > + unsigned long long param = args[0]; > + trace_seq_printf(s, "the helper was called, with argument %lld", param); > + return 0; > +} > +... > + if ( tep_register_print_function(tep, > + process_custom_helper, > + TEP_FUNC_ARG_STRING, > + "custom_helper", > + TEP_FUNC_ARG_LONG, > + TEP_FUNC_ARG_VOID) != 0) { > + /* Failed to register my process_custom_helper function */ > + } > +... > + if (tep_unregister_print_function(tep, process_custom_helper, > + "custom_helper") != 0) { > + /* Failed to unregister my process_custom_helper function */ > + } > +-- > + > +FILES > +----- > +[verse] > +-- > +*event-parse.h* > + Header file to include in order to have access to the library APIs. > +*trace-seq.h* > + Header file to include in order to have access to trace sequences related APIs. > + Trace sequences are used to allow a function to call several other functions > + to create a string of data to use. > +*-ltraceevent* > + Linker switch to add when building a program that uses the library. > +-- > + > +SEE ALSO > +-------- > +_libtraceevent(3)_, _trace-cmd(1)_ > + > +AUTHOR > +------ > +[verse] > +-- > +*Steven Rostedt* , author of *libtraceevent*. > +*Tzvetomir Stoyanov* , author of this man page. > +-- > +REPORTING BUGS > +-------------- > +Report bugs to > + > +LICENSE > +------- > +libtraceevent is Free Software licensed under the GNU LGPL 2.1 > + > +RESOURCES > +--------- > +https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git